Thermal relay



Nov.l 1, 1932. G, w, 'O'KEEFFE 1,886,354

THERMAL RELAY Filed May 18, 1929 Mgmt? 'X la:

W w. nfl/0461 KM cuit can Patented Nov. 1, 1932 UNITED STATES PATENTOFFICE GEORGE W. OKEFFE, OF MILTON, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPO- RATION lOIE MASSACHUSETTS THERMAL RELAY Application filed May 18,

rlhis invention relates to thermal relays of the type having an 'electrically-heated eX- pansible element which operates to control an electric circuit which, usually, is auxiliary to a. power circuit. rlhe relay is especially adapted to lie actuated by overload currents in a nio circuit and the like to protect the motor inst overloads.

ne objects of the present invention fision of a thermal relay wherein lary circuit controlled hy 'the eX- eienient is entirely electrically indeoi' the power circuit that heats the .c element so that the auxiliary cirr operated at a different voltage than that of the power circuit. This object ot' the invention is particularlydesirable for the control and protection of motor circuits which may he operated at, say, sin hundred volts and permits the auxiliary circuit which controls the switch of the motor circuit to he. operated at a lower and often more convenient potential as, for instance, 110 volts.

fr further object of the invention is the propansible pendent expansii vision oi a thermal relay having very simple and effective means by which the setting;r of the relay can be adjusted to operate in accordance with various different conditions.

Another object ol" the invention is the provision of a thermal relay ot the tubular or cartridge type wherein the casing is longitudinally divided into twoparts, and.' wherein the thermally expansible member and associated parts are carried by one oil the sections et the enclosing' casing.

A further object of the invention is the prorision ot a thermal relay having a thermally expansihle member and an electric heatingelement which is extended alongside but is tree from electrical connection with the eX- pansilole element.

nther ohjiec't ot the invention is the provision or a thermal relay having means so arranged that when once the relay hasA operated it can not again operate until reset; and a further object is to provide manual resetting means for such relay.

A yet further object of the invention is the provision of a thermal relay having` a novel 1929. Serial No. 364,149.

type. of separable contacts that are adapted to separate rapidly.

Another object of the present invention is to provide a long lui-metallic thermo-responsive strip so that it has a. good amount 0i" movement when subjected to the working variations in temperature and to fold the strip into one or more reliexed portions so that the long strip will occupy a. small space in the enclosing casing; and to arrange the heating' element for the strip so that it imarts heat to all of the reliexed portions thereof.

A further object of the invention is generally to improve the construction and operation or'l thermal relays.

Fig. l is a side elevation of the thermal relay embodyingthe invention.

Fig. 2 is an end elevation orP the relay and the supporting base therefor.

llig. 3 is a longitudinal sectional elevation of Vthe relay taken along line 3 3 of Fig. l.

Fig. l is' a longitudinal sectional view of one orn the sections of the relay taken along the line of engagement of the two sections.

F 5 is a view of the left hand end of the relay of Fig. l.

Figs. 6 and are perspective views ot the two sections of the easing.

Fig. 8 is a perspective view of the electrical heatingT element.

llig. 9 is a perspective view of the thermally-ezrpansihle element.

llig. l0 is a diagram illustrating the manner of associating the and auxiliary control circuits of an electric switch.

li is a modied form adapted for automatic resetting eration thereof.

The relay here shown includes a tubular enclosing casingv of the so-called cartridge type consisting of two complemental insulating sections l0 and which engage each of the relay 'after an opother along the longitudinal axis of the cas- 95 ing. The casing has the square intermediate portion lll and cylindrical end portions 16 and 18, each casing section thus being semicylindrical at its ends. Metal ferrules 20 and 22 are received on the cylindrical ends relay with the power strip of thermostatic metal which is composed of two metals of different co-efiicients of expansion secured together b'ack-to-back. The legs 32, 34 of said element are in spaced parallel relation and, in Fig. 3, the leg 34 is longer than the leg 32, although this is not necessarily the case. The leg32 is provided with a longitudinally extended slot 36 therein and is adapted to support a movable contact member. The contact member includes a flat plate 38 and is slidable over the outer face of the leg 32.

. element expands under heat,

Said plate is longitudinally movable within a slot 40 in the casing section 10 and extends through the end of said slot and is provided with an insulated handle piece 42 at the extended end thereof. The metal plate is a close fit Within the slot so that it is guided for movements longitudinally of the relay and is held 'against undue lateral movement. A pin 44 is fixed to said contact member and extends loosely through the slot 36 and has an enlarged head 37 which overlies the vslot and thus holds the plate on the thermal element. A retractile spring 46 engages said pin Iand the end of the thermal element, between the legs thereof, thereby biasing said movable contact for movement in a circuitopening direction toward the left, Fig. 3.

The casing section l0 is provided with a fixed terminal 48 that is located onVV one of the fiat sides of the casing land is fixed there in and has an inner cylindrical terminal 50 that constitutes a fixed contact/member of the auxiliary circuit. Said Contact member normally is received in an aperture 52 in the movable contact member 38 and thereby re- -strains said member from movement under the urge of its spring 46.- When the thermal the leg 32 is adapted to refiex toward the leg 34 and thus to move the movable contact member 38 out of engagement with the fixed contact member 50.

When this happens the movable contact member is moved rapidly toward the left and thus rapidly breaks the circuit with said fixed contact member. The movable contact member is so arranged that after it has been moved sufiiciently to clear the end of the fixed contact member 50, the upper surface thereof will ride over the end of said contact member and break the circuit therewith only at the downturned end 54'of the movable contact member. Thus any circuit interruptwhich is received onr ing arc is drawn only at the end of the movable contact member which at the time isv rapidly to a circuit opening posi' ment is carried by the section l2 'of the casing and is provided with means by which it canv be held in a plurality of positions with re# spect to the fixed contact member so that the setting of the relay can be varied. To this end, a generally flat supporting spring 56 1s fixed at itslmiddle to the outer face of the leg 34 and has depending ends which engage and bear upon the fiat bottom wall of the recess 28 in the casing section. A metal boss 58 which constitutes a second fixed terminal for the control circuit of the relay is carried by one of the flat faces of said casing section opposite the xed terminal 48. Said boss has a recess therein which contains a screw 60 that is screw-threaded in the end of the leg 34 of the thermal relay in the middle of the spring 56. Thus, by rotating the screw 60 in the proper direction, the spring 56 will be compressed and consequently the leg 32 will be moved away from the fixed contact member 50. Thus, by varying the position of the thermal relay with regard to the fixed contact member, the setting of the relay can be varied. The vspring and the screw give a firm and steady support to the thermal element in any setting thereof. The head of the screw is` sunk below the end of the boss 58 and preferably is sealed by a mass of solder 62 so that the setting can not readily be altered after it has once been made. The thermally expansiblel element is heated by a heater element which is electricallyindependent of the expansible element. The heater element is made from a fiat strip of resistance material which, especially for operationbat small currents, is stamped out to constitute a grid 64 having conductin portions which provide a relatively long pat of travel for the current traversing the grid,A

thereby to impart a substantial amount of resistance to the grid. The ends of the grid are provided with reflexed terminals forming the spaced legs 66 and 68, the legs 68 having the slots 70` therein. The heating portionof the grid is received within longitudinally-extended complemental grooves 72 in the two portions of the casing, which' ooves are disposed beside and are parallel with the grooves 26 and 28 and are separated therefrom by a wall of insulation 74. windovsT 76 having complemental parts located. m both casing sections is formed in lud I LA.

the grid terminals.

said wall 74 so that the heat of said grid is communicated readily to the thermally expansible element. Preferably, electrically insulating strips, as mica, 7 8 are located on opposite sides of the grid so as to insure the maintenance of insulation between the grid and the thermal element.

The terminals of the grid are located in complemental recesses formed in the cylindrical ends of the casing sections under the end ferrules. Said terminals are secured electrically and mechanically to said furrules by screws 82 which are passed through said ferrules and also through the slots 70 in the end terminals and are screw threaded 'into plates 84 which are located between the legs 66 and 68 of the terminals. Said screws are preferably soldered to the ferrules so that they will not accidentally become loosened. The end ferrules under the screws are also provided with a flattened section 86 which engage the flat face of the legs 68 of These flattened Sections also hold the ferrules against rotation on the ends of the casing.

With this construction, it is apparent that the circuit between the end ferrules and the heaterv element is electrically independent of the circuit through the terminals 48 and 58 and the thermal element so that the auxiliary circuit controlled by the thermal element can be energized at a potential that is different from that which supplies current t0 the heater element.

The thermal relay is adapted to be supported in a suitable base such as that shown in dotted lines, Fig. 2, which bas-e includes the insulating supporting plate 88 and the fuse clip terminals 90 carried thereby which eugage the end ferrules of the relay in the usual manner. Additional resilient contact members 92 are located between said fuse clips and are adapted to engage the terminals 48 and 58 of the control circuit of the relay.

One manner in which the relaycan be used is illustrated in Fig. 10. As here shown, the clectromagnetically operated switch has a movable switch member and a eooperating stationary switch member 102 which is in series with the power circuit 104 to be controlled by the switch, which circuit may con-- trol the operation of a motor, not shown. The swi tch is closed and held closed by the electro-A magnet 106 which is energized from the auX- iliary control circuit 108. This circuit is entirely independent of the power circuit and may be at a different potential therefrom. The circuit has the usual normally-open starting switch 110 -and the normally-closed stopping switch 112 which control the closing and opening respectively of the switch and the starting and stopping of the motor. As here shown, two thermal relays of the type above described and as indicated by the numeral 114 have their heater grids 64 only one being here shown) in series with the power circuit. The thermal elements of the relays normally shunt the starting switch 110 and when there is an overload in the powei` circuit open the circuit of thev elcctromagnet and cause the switch to open.

The modified form of thermal relay illustrated in Fig. 11 is essentially the same as that above disclosed but is without provision for holding the auxiliary circuit open until reset. T he upper leg 32 of the thermal element is provided with a contact member 88a which cooperates with the inner end of the terminal 48. The leg 32 is adapted to flex away from the terminal 48 -to break the control circuit. When the thermal element has cooled oiln sutliciently, however, it will again make contact with said terminal.

lclaim:

1. A thermal relay including an enclosing casing having a pair of main-circuit terminals carried by the. ends of said casing, a heating element carried by said casing and connected between said terminals, a pair of opposed auxiliary-circuit terminals carried by said casing between and insulated from said maincircuit terminals, and a U-shaped thermallyexpansible member heated by said heating element and having one leg connected to one i of said auxiliary circuit terminals and having its other leg controlli-ng the connection between said auxiliary-circuit terminals.

2. A thermal relay including an enclosing casing having a pair of main-circuit terminals at the ends thereof, an electric heating element carried by the casing and connected between said main-circuit terminals, a pair of auxiliary-circuit terminals carried by said casin g between and electrically separate from said main-circuitterminals, and a U-shaped thcrmally-expansible member having a fixed end connected with one of said auxiliary terminals and a contact engageable with the other auxiliary terminal for controlling the connection between said auxiliary-circuit terminals and arranged in heat-receiving relation with and electrically-insulated from said heating element.

3. A thermal relay including an insulating enclosing casing of the cartridge type having ferrules at the ends thereof constituting'mainline terminals, an electric li-eatin g element car ried by the casing and connected between sai d main-circuit terminals, auxiliary-circuit terminals carried by said casing on opposite sides thereof between and insulated from said ferrules, and a thermally-expansible member contained within said casing and controlling the connection betweenl saidterm'inals an d electrically insulated from and disposed in I' leg having a fixed connection to one of said auxiliary terminals and the free end of the other leg being movable toward and away and in heat-receiving relation with and in-- sulated from said heating element and controlling the connection between said auxiliary terminals.

5. In a thermal relay, a fixed contact member, a thermally-expansible member which cooperates at one end with said fixed contact member, and resilient supporting means for the other end of said .expansible member which is movable toward and away from said fixed contact member including means to adjust said expansible member bodily and in a straight line toward and away from said fixe-d contact member, and spring means acting on said latterend of said'expansible member on opposite sides of said adjusting means in a direction to urge it'toward said fixed contact member.

6. In a thermal relay, a fixed contact member, a thermally-expansible member having one end which cooperates with 'said fixed contact member, and resilient means which supports said expansible member for bodily movement toward and away from said fixed contact member including a supporting screw having a screw-threaded engagement with the other end of said expansible member, and a spring which acts on said expansible member on both sides of its screw-threaded connection with said screw.

7. In a thermal relay, a fixed contact member, -a thermally-expansible member having one end cooperating withsaid fixed contact member, a leaf spring secured at itsv middle to the other end of said expansible member and having its free ends bearing against a fixed support, and a fixedly-supported adiusting screw having its end screw-threaded into the last-named end of said expansible member between the ends of said leaf spring, whereby said expansible member can be adl justed toward and away from said fixed contact member. f

8. In a thermal relay, a ixedcontact mem; ber, a U-shaped thermally-expansible member A having a contact on one' leg cooperating with said fixed contact member, and resilient supporting means for the other leg of said expansible memb'er including a spring acting thereon under said contact in a direction to urge said expansible member bodily toward said fixed contact member, and adjusting means acting on said other leg under said contact to -vary the expanded position of said spring, whereby to vary the relation between said expansible member and said fixed contact member.

9. In a thermal relay, a fixed Contact mem.- ber, a U-shaped thermally-expansible member having oneleg cooperating with said Yfixed contact member, and supporting means for the other leg of said expansible member, including a'leaf spring fixed at its middle to sai-d other leg of said expansible member, a support against which the free ends of said spring bear, and a screw carried by said support engaging said spring in the middle thereof to Vary the expanded position thereof,

. whereby to vary the relation between said expansible -member and -said fixed contact member.

1Q. In a thermal relay, a fixed contact member, a U-shaped thermallyexpansible member having one leg cooperating with said fixed contact member, and supporting means for the other leg of sai-d expansible member including a leaf spring fixed at its middle to said other leg of said expansible member, a support against which the free ends of said spring bear, and a screw carried by said sup` port engaging said spring in the middle thereof to vary the expanded position thereof, whereby to vary the relation between said expansible member and said fixed contact member, said screw also constituting a circuit terminal for said thermally-expansible member. 1

l1. In a thermal relay, an insulating enclosing casing having a recess therein, circuit terminals carried by said casing on opposite sides thereof and in the same line, a U-shaped thermally-expansible member located in the recess of said casing having one leg thereof cooperating with one'of said circuit terminals and having the other leg overlying said other circuit terminal, a screw carried by said other circuit terminal and threaded in said overlying leg of said expansible member, and a leafspring fixed at its middle to said other leg about said screw and having its free ends bearing on the wall of said recess on oppositesides of said screw.

12. In a thermal relay, a thermally-expansible element having/a flat face, a movable contact member secured to and movable with said element and also slidable on said flat face in a circuit-opening direction` means acting on said movable contact member to move it in a circuit-opening direction, and a fixed Contact member cooperating with said movable contact member to hold it in circuit-closing engagement therewith.

13. In a thermal relay, a thermally-expansible membcr having a flat face, a movable contact member including a flat member which is secured to and is slidable over said fiat face, means to move said movable contact member in a circuit-opening direction over said fiat face, means cooperating wth said expansible member to guide said movable-contact member for such movement, and a, fixed contact member engageable with a part of said movable contact member to hold it releasably for movementin ya circuit-opening direction.

14. In a thermal relay, a U-shaped thermally-expansible member having supporting means for one leg, the other leg being free to expand toward and away from said supported leg, a movable contact member including a metal plate which is secured to and is supported by and is slidable lengthwise on said unsupported leg, means urging said plate for sliding movement in a circuit-opening direction, and a fixed contact member fitting in a recess of said plate to hold it releasably in circuit-closing yengagement therewith.

15. In a thermal relay, an enclosing casing, ferrules constituting line terminals arranged on the opposite ends of said casing, a heater element located within the casing and connected between said ferrules, auxiliary circuit terminals carried by said casing between and insulated from said line terminals, separable contact members contained within said easing each having an electrical connection with a separate one of said auxiliary terminals, means including a thermally-expansible member heated by said heater element arranged to eii'ect the separation of said contact members, and means including a resetting member extended externally of the casing and through and insulated from one of said ferrules having meansvto effect the resetting of said contact members.

16. In athermal'relay, the combination of an enclosing casing, end errules thereon constituting line terminals, a heater element connected therebetween, a fixed contact member carried byy said casing between said ferrules,

-a thermally-expansible member influenced by said heater element, and a contact member mounted upon and movable on said thermally-expansible member into and out of engagement with said fixed Contact member, said movable contact member having an extension which extends through one of said ferrules and is insulated therefrom and is located externally of said casing when said contacts are separated by which said movable contact member can be restored into engagement with said fixed contact member.

17. In a thermal relay, the combination of an, enclosing casing, a U-shaped thermallyexpansible member located therein having fixed supportingmeans for one of its legs, the other leg being free to flex, a fixed contact member, a movable Contact member cooperating therewith including a plate which plate and said fixed is slidable on the free leg of said thermallyexpansible member, said leg having a longitudinally-elongated slot therein and said plate having a. pin which is extended through said slot, and a retractile spring connected with and extended between said pin and that 'part of said expansible member which connects said legs.

18. In a thermal relay, the combination of an enclosing casing, a U-shaped thermally-expansible member located therein. having fixed supporting means for one of its legs, the other leg being freek to flex, a fixed cont-act member, a movable contact member cooperating therewith including a plate which is slidable on the free leg of said thermally-expansible member, said leg having a longitudinally-elongated slot therein and said plate having a pin which is extended through said slot, and a retractile spring connected with and extended between said pin and that part of said expansible member`which connects saidv legs, said-plate having an extension that is located externally of said casing and constitutes a resetting member by which said plate can be restored to the engagement of said fixed contact member after it has been moved away therefrom. .t

19. In a thermal relay, the combination of an enclosing casing of insulating material having ferrules on the ends thereof which constitute line terminals, an electric heater element located within the casing and connected between said ferrules, a U-shaped thermally-expa-nsible member located Within said casing electrically free from but in heat-receiving relation with said heater element, said U-shaped expansible member having a Jsupported leg and a leg which is free to flex, a fixed contact member located adjacent said free leg, supporting means for said fixed leg having means to support said expansible member in any one of a plurality of p ositions-with respect to said xed contact member, a movable contact member including a plate which is slidable on said free leg, said contact member having interconnecting parts which normally hold them in engagement, amspring acting upon said plate to move it in a circuit-opening direction away from said fixed contact member when said plate and said fixed contact member are disengaged, saidn plate having a part which is extended externally of said casing through one of said errules and constituting a resetting member by which said plate can be restored to the engagement of said fixed contact member.

20. In a thermal ing casing, circuit-controlling members inleluding a thermally-expansible member carried by said casing, and an electric heating element for said thermally-expansible member having aheat generating portion thereof which is extended lengthwise of said casing relay, a two-part enclos` and which is extended across the connection between and is located in both parts thereof.

21. In a thermal relay, -a two-part enclosing casing, circuit-controlling elements including a thermally-expansible member carried by said casing, the two parts of said casing being separated by a line of separation which is extended lengthwise of the casing, and an electrical heating element for said thermally-expansible member having a heat dissipating portion extended lengthwise of said casing and across said line of separation.

22. In a thermal relay, anlinsulating enclosing casing composed of two superimposed sections, said sections having complemental recesses therein which constitute a heater compartment common to both casing sections, an electric heater located in both recesses of said compartment, and a circuitcon4 trolling device including a thermally-expansible member carried by said casing and located in heat-receiving relation with said heater element.

23. In a thermal relay, an insulating en' closing casing composed of two superim- Y posed sections having pairs of complemental' recesses forming a pair of compartments located side by side, an electric heating element located in one of said compartments, and circuit controlling elements including a thermally-expansible member located in said other compartment` in heat-receiving relation with said heating element.

24. In a thermal relay, an insulating enclosing casing composed of two superimposed sections having pairs of complemental recesses forming a pair of compartments, an electric heating element located in one of said compartments, and circuit controlling elements including a thermally-expansible member located in said other compartment in heat-receiving relation with said heating element, said last-named compartment having an opening to the exterior o said casing through one end thereof, and resetting means for circuit controlling element extended `through said opening and terminated externally 'of said casing.

In testimony whereof, I have signed my name to this specification.

A GEORGE W. OKEEFFE. 

